1. Field of the Invention
The present invention pertains to methods and apparatus for locating leaks in pipelines. More specifically, the present invention pertains to methods and apparatus for locating small fluid leaks at undetermined locations in a pipeline, especially those of a magnitude not easily detected by other methods.
2. Brief Description of the Prior Art
Increased awareness of environmental, safety and financial consequences of petroleum and petroleum products leaking from pipelines has heightened the demand for accurate methods and apparatus for detecting and determining the location of pipeline leaks. Most pipelines are buried in the ground and, unless the leak is large enough to be visible from the surface of the ground or the air, may not be easily detected. This is especially true for very small leaks. Although small leaks may not be as hazardous as large ones, environmental, safety and financial consequences are still of great importance.
The typical method for determining if there is a leak in a pipeline is hydrostatic testing where fluids, such as water, are placed in the section of pipeline under observation. The pipeline section is closed at both ends and the fluids are pressurized therein. Pressure and temperature measuring devices are monitored over the next several hours to indicate whether there is a leak or not. However, even though declining pressure may indicate a leak, a leak may be so small as not to be readily located.
A number of pressure, volume and flow measuring techniques have been developed for determining and locating leaks in pipelines. However, none of them appear to be totally effective in accurately locating very small pipeline leaks. The industry continues to search for more effective and efficient methods and apparatus for doing so.
The present invention provides a method and apparatus for locating leaks at an undetermined location in a section of pipeline of known length. A standard pressure vessel of relatively small volume is provided at each end of the pipeline section and connected to respective ends of the pipeline section through a valve. The section of pipeline is closed at each end and the valves into the standard pressure vessels are opened. Fluids, whether they be water or other fluids, are placed in the pipeline and the standard pressure vessels under a pressure of at least a predetermined level. Then the valves to both of the standard pressure vessels are simultaneously closed, isolating each of the standard pressure vessels from the pipeline section so as to maintain the pressure vessels at substantially the same level as at the time of closing. The differential pressure between each end of the pipeline and its respective standard pressure vessel is then continuously monitored and recorded in real time measurements and, if there is a leak, the location of the leak is determined by solving an equation, based on the equilibrium equation and real time measured differential pressure values at each end of the pipeline.
Apparatus for performing the method of the present invention includes, in addition to the standard pressure vessels and associated valves at each end of the pipeline, differential pressure measuring means at each end of the pipeline and means for continuously monitoring and recording the differential pressures. In a preferred embodiment, the apparatus includes a computer which is programmed to solve an equation for determining the distance of a leak from one end of the pipeline section by utilizing the real time measured differential pressures. Preferred embodiments also include transmitters operatively connected to the differential pressure means at each end of the pipeline and a receiver remotely located with and connected to the computer to effect simultaneous real time input from the differential pressure means at both ends of the pipeline section for processing by the computer.
With the method and apparatus of the present invention, the location of a leak can be accurately determined within a relatively short period of time. The apparatus for performing the method requires accurate instruments. However such instruments are readily available with today""s technology. The components of the apparatus are simply configured, installed and operated. Other objects and advantages of the invention will be apparent from reading the description which follows in conjunction with the accompanying drawings.